AWS Lambda, Serverless, FaaS - there is a lot of noise around those topics online (and for a very good reason!) and it can get confusing at times 🤯

In this collection we're going to take a look at AWS Lambda from scratch, in order to get **YOU** from:

"_I have no idea what a lambda function is_" 

to 

"_I know quite a bit about AWS Lambda, and I'm going to use it to solve my problems_"

Checkout the [community notes for this collection on github](https://github.com/theianjones/egghead.io_learn_aws_lambda_from_scratch).

AWS Lambda, Serverless, FaaS - there is a lot of noise around those topics online (and for a very good reason!) and it can get confusing at times.

In this quick 2 minute lesson we're going to cover what exactly is AWS Lambda, what's the Lambda pricing model (e.g. what's included in the free tier), what programming languages can be used with Lambda and also - what does it mean for something to be "serverless"

WTF is AWS Lambda?

In this quick lesson we're going to learn how to create a brand new AWS Lambda function from scratch and show how to test the execution of a 'hello world' Lambda function

Create an AWS Lambda function from scratch

Once the AWS Lambda function is created in AWS Cloud, we'd like to be able to call it outside of the AWS Console

In order to do that - we need to create a trigger.

In this lesson we're going to learn how to create an API Gateway trigger and attach it to a AWS Lambda function so the function will get triggered once an HTTP request is sent to this API.

Add an API Gateway trigger to a AWS Lambda function to create a REST API

Since AWS Lambda functions are running in the cloud, we need to be able to dig in to see what's going on in there (especially when we have issues with the function).

This is where logs come in, AWS Lambda allows us to send logs from functions to various services, including CloudWatch

In this lesson we're going to learn how to add logs to a lambda function and how to review them in CloudWatch

Add logs to AWS Lambda function and review them in CloudWatch

AWS Lambda functions can be triggered by many different sources, including HTTP calls and files being uploaded to S3 buckets.

This can be useful, for instance if we'd like to start processing a file using a lambda function whenever it gets uploaded to an S3 bucket.

In this lesson we're going to learn how to create a S3 event trigger for a lambda function, how to create an S3 sample event to test the function and how can we verify that the function was triggered when uploading a file by viewing CloudWatch logs.

Trigger an AWS Lambda function by uploading a file to an S3 bucket

Secrets are meant to be... well, secret.

We should do whatever we can not to expose important secure keys (like database passwords) to the outside world.

As such, hardcoding passwords inside of your source code is a terrible idea.

Luckily, with AWS Lambda we can avoid that - in this quick lesson we're going to learn how we can use environment variables in order to pass in a password to a lambda function without potentially exposing it to the world.



Use environment variables in an AWS Lambda function

It's awesome that we can edit a lambda function either directly in the AWS Console, or by uploading a new zip file or uploading it to an S3 bucket whenever we want.

Although at some point we'd like to effectively "freeze" a function to ensure that no one can modify it anymore, for instance when we want to deploy this function to a production environment.

In this lesson we're going to learn how to create different immutable versions of an AWS Lambda function, how to switch between them and how to call them separately

Create different versions of an AWS Lambda function

Every AWS resource has a unique ARN - Amazon Resource Name.

This is true for AWS Lambda function versions as well, which means that every single time we publish a new version of a function, we'd need to update our backend to point to this new ARN.

In this lesson we're going to learn how to create an alias for an AWS Lambda function so we're able to do following things without having to update any code calling the function:

- Update the function with a new version while keeping the same ARN pointing to it
- Have a single ARN that once executed is going to call either one of two versions by having a random 50/50 split - useful for A/B testing on production

Create an alias for an AWS Lambda function

Web developers tend to use external dependencies (e.g. npm packages) quite often, and lambda functions are not exception - there's no need to reinvent the wheel if we can use a package created by someone else.

In this lesson we're going to learn how to create a Lambda Function Package in order to create and deploy an AWS Lambda function which uses an external dependency - axios

Use external dependencies in an AWS Lambda function

Our AWS Lambda functions may take some time to execute, especially when they are going to call external APIs etc.

The default timeout is 3 seconds, which may not be enough.

In this lesson we're going to learn how to modify the default timeout for an AWS Lambda function as well as how to use the `context` object provided with each lambda call in order to see how much time is remaining before a function timeouts.

Modify the default AWS Lambda function timeout 

AWS Lambda functions can be triggered by a number of sources, for instance an asynchronous HTTP request. We may want to be a bit more synchronous - for instance trigger a function every X minutes, hours or days.

In this lesson we're going to build a simple "clock" function which is going to log the current time to CloudWatch logs every minute using rate expressions

Use CloudWatch event to execute an AWS Lambda function with a fixed interval

AWS is not awesome because of Lambda, S3, DynamoDB, IAM and other services.

It's awesome because you get to *combine* them together in order to solve your problems.

In this lesson we're going to learn how to use IAM roles and policies effectively in order to allow an AWS Lambda function to list all S3 buckets using the `aws-sdk` `listBuckets` method. 

We're also going to learn what's the [principle of least privilege](https://docs.aws.amazon.com/IAM/latest/UserGuide/best-practices.html#grant-least-privilege) in AWS



Learn AWS Lambda from scratch

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